GB2187324A

GB2187324A - Tape recorder synchronizer apparatus

Info

Publication number: GB2187324A
Application number: GB08604987A
Authority: GB
Inventors: William John Murray; Robin Lucien Lince
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1986-02-28
Filing date: 1986-02-28
Publication date: 1987-09-03
Also published as: GB8604987D0; GB2187324B

Abstract

A tape recorder synchronizer apparatus comprises a video tape recorder (VTR) 1 and an audio tape recorder (ATR) 2, the respective outputs from which are to be controlled to be in synchronism, each of the VTR 1 and the ATR 2 supplying positional data such as timecodes relating to the reading position of a tape in the VTR 1 or ATR 2, a synchronizer 4 to which the positional data are supplied, and a controller 3 for controlling the reading position of the VTR 1 and the ATR 2, wherein the controller 3 issues commands to the synchronizer 4 which in dependence on these commands and the positional data received from the VTR 1 and the ATR 2, issues respective commands to the VTR 1 and the ATR 2. <IMAGE>

Description

SPECIFICATION Tape recorder synchronizer apparatus This invention relates to tape recorder synchronizer apparatus. More particularly, but not exclusively, the invention relates to tape recorder synchronizer apparatus for synchronizing a video tape recorder (VTR) and an audio tape recorder (ATR).

The need to synchronize a VTR and an ATR arises in a number of circumstances, such as in editing, and it is often necessary for the synchronism to be precise, for example to achieve a so-called lip-sync, where spoken words must be synchronized with lip movements.

The synchronization of a VTR with an ATR is made difficult by the different constructions which the two machines commonly have. This gives rise to individual characteristics in respect of parameters such as tape acceleration and deceleration, the maximum tape speeds in the forward direction and the reverse direction, and the transport delay, that is the delay between receipt of a command and start of the commanded action. These characteristics of tape recorders are known as the ballistics of the machines.

Hitherto the normal method of operating a VTR and an ATR in synchronism has been to designate one tape recorder as the master and the other tape recorder as a slave. An example of such a method is disclosed in "Concept and Realization of a Modular Edit Code Synchronizer" presented by Tom Sharples at the 76th Convention of the Audio Engineering Society in New York from 8 to 11 October 1984. In such a method the slave tape recorder must endeavour to follow the actions of the master tape recorder by "chasing" the timecode produced from the master tape recorder's prerecorded track. Inevitably, there is some delay during which the slave tape recorder must determine in dependence on the received timecodes, the mode (play or shuttle for instance) of the master tape recorder, and the direction and speed of the tape of the master tape recorder.Additionally, the relative ballistics of the two tape recorders may be such that it is not possible for the slave tape recorder to follow the master tape recorder closely. For example, if the master tape recorder is rewinding at full speed, the slave tape recorder may not be able to rewind at such high speed, and will therefore arrive at a predetermined timecode sometime later than the master tape recorder. This gives rise to operational problems.

According to the present invention a tape recorder synchronizer apparatus comprises: first and second tape recorders, the reproduced outputs from which are to be controlled to be in synchronism, each said tape recorder having means for supplying positional data relating to the reading position of a tape in said tape recorder; a synchronizer to which said positional data from each of said tape recorders are supplied; and a controller for controlling the reading position of said first and second tape recorders; wherein said controller issues commands to said synchronizer which in dependence on said commands received from said controller and said positional data received from each of said tape recorders, issues respective commands to each of said tape recorders.

Thus in embodiments of apparatus according to the present invention, neither of the tape recorders is permanently designated as a master tape recorder or a slave tape recorder, and the synchronizer is able to issue commands to both the tape recorders in consideration not only of the positional data received from the tape recorders, but also, for example, in dependence on the respective ballistics of the tape recorders, so enabling more accurate synchronism to be maintained.

The invention will now be described by way of example with reference to the accompanying drawings, the single figure of which shows an embodiment of tape recorder synchronizer apparatus according to the present invention.

The tape recorder synchronizer apparatus comprises a first tape recorder 1, which in this embodiment is a VTR, and a second tape recorder 2, which in this embodiment is an ATR. In this description the term ATR is used simply to described a tape recorder which is capable of recording and reproducing audio data, and in fact the ATR 2 may be basically a VTR with an adapter to enable pulse code modulated audio data to be recorded on the tape in a similar format to that usually used for video data.

In an alternative embodiment, both the first and the second tape recorers may be VTRs for video.

The apparatus also comprises a controller 3 which issues commands, which may be in the form of 8-bit serial commands, to a synchronizer 4, which in turn issues respective commands to the VTR 1 and the ATR 2. The commands issued to the VTR 1 may be in the form of 8-bit serial commands, and the commands issued to the ATR 2 may be similar or may be in the form of parallel data. Status data concerning the VTR 1 and the ATR 2 are supplied back to the synchronizer 4, and from the synchronizer 4 back to the controller 3, at least in respect of the VTR 1. The synchronizer 4 also receives respective positional data relating to the reading position of the respective tape from the VTR 1 and the ATR 2.

This positional data will generally be timecode data, for example of the format laid down by the European Broadcasting Union or the Society of Motion Picture and Television Engineers. Such timecodes may be recorded and reproduced from longitudinally-extending tracks on the tape or in oblique tracks on the tape, for example in the vertical intervals of video signals or of signals which have been recorded in video format. Alternatively, the positional data relating to the reading position of the tape may be derived from the tape transport mechanism of the VTR 1 and/or the ATR 2, for example by counting longitudinal tachometer pulses derived from the mechanism.

When commanded by the synchronizer 4 to reproduce, the video data reproduced by the VTR 1 is supplied by way of a video switch 5 to a recording VTR 6, and likewise when the ATR 2 is commanded by the synchronizer 6 to reproduce, the reproduced audio data is supplied by way of an audio mixer 7 to the recording VTR 6. The controller 3 also issues commands to the recording VTR 6, and to the video switch 5 and the audio mixer 7.

Optionally, the VTR 1 may also supply positional data, such as timecodes, to the controller 3.

Although the commands issued by the synchronizer 4 to the VTR 1 and to the ATR 2 will normally be ordinary commands such as stop or play or rewind at a certain predermined speed, other commands may also be issued.

The operation will now be described.

In this tape recorder synchronizer operation, neither the VTR 1 nor the ATR 2 is permanently designated as the master or a slave.

Commands originate from the controller 3, but pass by way of and are interpreted by the synchronizer 4. The inputs on which the synchronizer 4 operates may be just the commands issued by the controller 3, and the positional data received from the VTR 1 and the ATR 2. This has the advantage that the ATR 2 does not need to wait for the operation of the VTR 1 to be interpreted by receipt of the positional data from the VTR 1 after a command has been issued to the VTR 1, but can itself be issued with a command at the same time that a command is issued to the VTR 1.

This means that when a command is issued to the VTR 1, the ATR 2 can simultaneously be commanded, so that synchronism between the ATR 2 and the VTR 1 is more likely to be closely maintained.

As a refinement, the synchronizer 4 can be made more intelligent by storing therein data relating to the known ballistics of the VTR 1 and the ATR 2. As an example, suppose that the VTR I is capable of rewinding at twice the speed of the ATR 2. If this data is stored in the synchronizer 4, then if the controller 3 issues a command to the synchronizer 4 to rewind the VTR 1 at full speed, the synchronizer 4 may interpret this as a command to rewind the ATR 2 at full speed, and the VTR 1 at half its full speed. In this way, the VTR 1 and the ATR 2 can be maintained more closely in synchronism. In this particular example it might be said that the synchronizer 4 has temporarily given the ATR 2 the role of master, and the ATR 2 the temporary role of slave. In other circumstances, where the ballistics differ, these roles may be reversed.

There are basically two ways in which the synchronizer 4 can be provided with stored information about the ballistics of the VTR 1 and the ATR 2. In the first case, where the VTR 1 and the ATR 2 are machines with known predetermined ballistics, the respective parameters such as maximum forward and reverse tape speeds, maximum acceleration and deceleration, and transport delay may be preprogrammed into respective programmable read-only memories (PROMs), which are incorporated into the synchronizer 4. In the second case, where the VTR 1 and the ATR 2 are machines with unknown ballistics, the synchronizer 4 likewise incorporates respective PROMs, but in this case the PROMs are programmed with the required parameters after the synchronizer 4 has been connected to the VTR 1 and the ATR 2.This is done by the synchronizer issuing predetermined commands to the VTR 1 and the ATR 2, and analyzing the resulting timecodes and states signals received from the VTR 1 and the ATR 2. For this purpose a large scale integrated circuit for reading the timecodes, and a counter for determining the corresponding time intervals may be used to derive the required parameters for storage in the respective PROM.

When the VTR 1 and/or the ATR 2 are commanded to reproduce, the reproduced data is supplied to the video switch 5 and/or the audio mixer 7, which are controlled by the controller 3 to supply the reproduced data to the recording VTR 6.

The control effected by the controller 3 can be refined by supplying the positional data from the VTR 1 to the controller 3.

Particularly if the synchronizer 4 is arranged such that the commands it issues to the VTR 1 and the ATR 2 are modified in dependence on the ballistics of the VTR 1 and the ATR 2, the effect of the tape recorder synchronizer apparatus as described is to match the ballistics of the VTR 1 and the ATR 2, so that to an operator the video data and the audio data appear to be originating from one tape recorder.

Claims

1. A tape recorder synchronizer apparatus comprising: first and second tape recorders, the reproduced outputs from which are to be controlled to be in synchronism, each said tape recording having means for supplying positional data relating to the reading position of a tape in said tape recorder; a synchronizer to which said positional data from each of said tape recorders are supplied; and a controller for controlling the reading position of said first and second tape recorders; wherein said controller issues commands to said synchronizer which in dependence on said commands received from said controller and said positional data received from each of said tape recorders, issues respective commands to each of said tape recorders.

2. Apparatus according to claim 1 wherein said positional data are timecodes read from said tape in the respective said tape recorders.

3. Apparatus according to claim 1 wherein said positional data are derived from a tape transport mechanism in the respective said tape recorder.

4. Apparatus according to claim 1, claim 2 or claim 3 wherein said tape in said first tape recorder carries video data.

5. Apparatus according to claim 4 wherein said first tape recorder also supplies positional data relating to the reading position of the tape in said first tape recorder to said controller.

6. Apparatus according to claim 4 or claim 5 wherein said tape in said second tape recorder carries audio data.

7. Apparatus according to claim 4 or claim 5 wherein said tape in said second tape recorder carries video data.

8. Apparatus according to claim 6 wherein said video data is reproduced from said first tape recorder and is supplied by way of a video switch for recording on a third tape recorder.

9. Apparatus according to claim 8 wherein said audio data is reproduced from said second tape recorder and is supplied by way of an audio mixer for recording on the tape in said third tape recorder in synchronism with the recording of said video data.

10. Apparatus according to claim 9 wherein said video switch and said audio mixer are controlled by said controller.

11. A tape recorder synchronizer apparatus substantially as hereinbefore described with reference to the accompanying drawing.

11. Apparatus according to any one of the preceding claims wherein said synchronizer stores information relating to the ballistics of said first and second tape recorders, and said commands issued by said synchronizer to said first and second tape recorders are modified in dependence on said stored data to maintain said first and second tape recorders more closely in synchronism.